1. Field of the Invention
The present invention relates to bioassays generally and, more particularly, but not by way of limitation, to a novel pipettor reservoir for use with particulate-containing liquids.
2. Background Art
In the field of biotechnology, particulate matter is used in a variety of assays. The most common particulate matter is the use of living cells. Other applications are the use of coated particles, such as magnetic beads or radioactive particles. In high throughput systems, it is necessary to pipette liquid containing this particulate matter from a source reservoir to a receiving bioassay plate. A problem encountered in such systems is that the particulate matter tends to settle out of the liquid in which it is suspended. A common method of overcoming this tendency is the use of a magnetic stir bar within the reservoir, driven by an external magnet drive assembly. Various shakers and vibrators are also used.
In automated pipetting systems, a constant level source reservoir may be used. This is a weir-type reservoir that is included within the flow path of a peristaltic pump. The fluid is kept in motion between a large source reservoir and the constant level reservoir by the peristaltic pump. The agitation created by the flow is relied on to keep the particulate matter in suspension in the liquid.
The constant level reservoir has a relatively small depth and the liquid level is kept constant by an overflow weir. This allows the pipettor system to go to the same depth in the liquid for aspiration of the reagents. For use with the industry standard, 96- or 384-well pipettors, the horizontal dimensions of the reservoir surface area must measure approximately 3.4×5.0 inch. Depending on the mass of the particles, the flow through the reservoir may not keep them in suspension. There are normally “dead” spots in the corners of the reservoir or other areas of the reservoir outside of the main liquid path. A multi-well pipettor, 96 or 384 wells, will aspirate uniformly over the entire 3.4×5.0-inch surface area; however, the “dead” spots in the reservoir will not provide a uniform aspiration of particles in all 96 or 384 pipettor tips. This has a detrimental effect on the results of the assay.
Also, there is an increasing use of paramagnetic particles in various bioassays and the use of a magnetic stir bar is prohibited in these applications.
Accordingly, it is a principal object of the present invention to provide a source reservoir for pipetting in which the problem of settling of particulate matter suspended in a liquid is eliminated or greatly reduced.
A further object of the invention is to provide such a source reservoir in which “dead” spots are eliminated or greatly reduced.
An additional object of the invention is to provide such a source reservoir having a constant velocity of liquid flow in the various feed-way passages thereof
Another object of the invention is to provide such a source reservoir that can be economically constructed using conventional manufacturing techniques.
Yet a further object of the invention is to provide a source reservoir that can be used satisfactorily with paramagnetic particulate materials.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figure.